Yes, in is a Scrabble word!
...and is worth 2 points in Scrabble, and 3 points in Words with Friends
in
Adverb
1. To or toward the inside of
Adjective
1. Holding office
2. Directed or bound inward
3. Currently fashionable
Noun
1. A unit of length equal to one twelfth of a foot
2. A rare soft silvery metallic element; occurs in small quantities in sphalerite
3. A state in midwestern United States